1. Field of the Invention
The present invention relates to screen displayed graphics and, more particularly, to measurement and value display arrangements therefor.
2. Description of Related Art
The prior art is replete with various systems in which information is at some point displayed graphically on a computer screen. Often the displayed information relates to events occurring over time. In such cases it has been found convenient to display the information in the form of a bar graph or waveform placed on a x-y coordinate system with the x-axis indicating time and the y-axis indicating number of events. Based upon the abscissa (horizontal coordinate obtained by measuring parallel to the x-axis) and ordinate (vertical coordinate obtained by measuring parallel to the y-axis) values of any displayed point on a bar graph or waveform, and based upon the scale of the x- and y- axes, meaningful information relating to number of events at a particular time is communicated by such displays.
Heretofore, programs presenting graphical information have generally been designed so that the user has to estimate abscissa and ordinate values of a point by "eyeballing" from the point to the x- and y- axis scales. Some programs have attempted to improve the accuracy of such readings by displaying a fixed rule (i.e., graph paper-like background) on the screen.
Both of these approaches are clumsy and time consuming to use and both produce inaccurate results. Although the "fixed rule" approach can help a user extract estimated values off of a distant scale, not infrequently it is troublesome to use in that the proper rule (of a number of rules) is "lost" as one attempts to "follow" it from a point to a scale.
In addition to the above-described general approaches, some programs heretofore have included more advanced arrangements for facilitating the determination of the value of a point, or the relationship between points, as indicated on, or could be determined with reference to, a distant scale.
In U.S. Pat. No. 4,751,504 to Slavin, for example, two cursors are used to determine the difference in positions of points on a waveform. According to the teachings of Slavin, a cursor interface for a waveform display provides for movement of a waveform relative to a first cursor. When the first cursor overlies a desired point on the waveform, the cursor can be "locked" to the waveform. Then, the first cursor and the waveform can be moved together relative to a second cursor. When the second cursor overlies another desired value on the waveform a measurement value can be displayed indicating the difference in positions on the waveform of the cursors.
Another approach may be seen in U.S. Pat. No. 4,730,262 to Watanabe et al. which teaches a scanning display including a plurality of bar graphs. The plurality of bar graphs have associated scanning and margin times, which are digitally displayed in conjunction with the graphical display of the bar graphs.
Notwithstanding the voluminous teachings of the prior art, nowhere is there disclosed or suggested a graphic value indicating system that uses a rule to facilitate determining information about a point in a coordinate system with reference to a distant scale, and which also uses a digital display to locate the rule. The absence of such a value indicating system is a shortcoming and deficiency of the prior art.